# The emf of cell $Zn/ZnCl_2(0.05mol\;dm^{-3})/Ag^+/AgCl(s)/Ag$ is 1.015V at 298K,the silver electrode being positive,while the temperature coefficient of its emf is $-0.00492VK^{-1}$.Write down the equation for reaction occuring when the cell is allowed to discharge and calculate changes in free energy(G)?

$\begin{array}{1 1}(a)\;-162.89KJmol^{-1}&(b)\;162.89KJmol^{-1}\\(c)\;195.89KJmol^{-1}&(d)\;-195.89KJmol^{-1}\end{array}$

The free energy change accompany the reaction is given by
$\Delta G=-nFE$
$n=2,E=1.01V,F=9650C\;mol^{-1}$
$\Delta G_{298}=-2\times 1.01V\times 96500Cmol^{-1}$
$\Delta G_{298}=-195Jmol^{-1}$
$\Rightarrow -195.89KJmol^{-1}$
Hence (d) is the correct answer.